Spark plug



April 28 1942- G. PARKIN `2,281,511

SPARK PLUG Filed July l, 1940 Patented Apr. 1942 UNITED STATES PATENT OFFICE George Pllllxgphia, Pa. f Application July 1, 1940, Serial No. 343,498

(ci. 12s-169) 4 Claims.

This invention relates to spark plugs and has for an iin-portantobject thereof the provision of a spark plug which may be readily adapted for use under highly variable conditions.

The use in the sametype of engine of varying types of fuels, andthe wide variation in the characteristics of different engines renders it ordinarily necessary to provide an extensive line ofdiierent types o f plugs in order that varying temperature conditions may be taken care of.4 If a plug is operating at too low a temperature, that is to say, it fails to heat to a certain degree during operation of the engine, the plug will foul or soot and eventually short circuit, causing faulty operation. If, on the other hand, th'e temperature of the plug becomestoo high, the value of the porcelain as an insulation is destroyed with resultant pre-ignition blow-by and burning of the electrodes.

In an attempt to control the temperature at which the plug operates, it has heretofore been the practice to vary the amount of the porcelain of the plug which is subjected to combustion temperatures in the cylinder, as many as eight or nine dierent types of porcelains being employed in the same size plug. Obviously, this must result in a considerable increase in the cost of individual plugs since a large and varied stock oi' plugs must be maintained at all times, and the porcelain of the ordinary plug is, obviously, one of the more expensive elements therein.

An important object of the present invention isthe provision of a plug construction such that made to answer under all conditions, and in which control of the temperature at which the plug is operating is obtained not from variation of the area of the porcelain which is subjected to engine temperatures, but by varying the size of a primary electrode to thereby control the extent of the combustion chamber within which the porcelain is disposed.

.for use in a given size a single porcelain may be Another object ofthe invention is` the sion in a spark plug oi an arrangement permitting ready radio shielding of the plug and which at the same time provides for insulation of the plug. against moisture. These and other objects I attain by the construction shown in-rrthe accompanying drawing wherein, for the pulDOse of illustration, Ihave shown a preferred embodiment of my invention and wherein:

Fig. 1 is a side elevation of a spark plug constructed in accordance with my invention; and

Figs. 2 and 3 are vertical sectional views illus'- trating the internal construction and the method of controlling the plug temperature.

Referring now more particularly to the drawing, the numeral Ill4 generally designates the bushing of the plug, the threaded lower end of which has at its inner end a bore II for the passage oi' the tip of a primary electrode I2, and is equipped with the usual secondary electrodes indicated at I3. Immediately above the lower end of the plug, the bore Il is enlarged, as at I4, the bore at this point being preferably cylindrical. and at a considerable distance -above the initial enlargement at Il is againv enlarged as at I5 to provide the usual seat Il for the reception of gaskets I'| upon which the lower portion I8 of the shouldered portion is disposed in suiliciently close relation to the wall of the bushing or shell to be in good heat exchange relation therewith. The porcelain is held in position through a ring nut I9 which, in turn, engages the upper shoulder of the porcelain through gaskets 20. Gaskets I1 and 20 are preferably of the type illustrated in Patent No. 1,987,024 to J. W. Parkin, gir., granted January 8, 1935, for Spark plug.

The porcelain is provided with a, depending, relatively thin skirt 2|. This skirt has an internal diameter substantially the same as that of the bore II and an external diameter which will bring its face into the closest. practical engagement with the walls of bore I4 so that any heat generated in -the combustion chamber 22 and transmitted to this procelain will be conducted away through the bushing to the relatively cool head of the engine. As will -be noted, the primary electrode is of large size and will be so under all conditions although the size of this electrode is varied to control thetemperature of the plug, and to this end the electrode, instead of being embedded in the porcelain, is threaded therein at its upper end, as indicated at 23. The

size of the combustion chamber and the extent .of the body oi this electrode will control temsa vided with a spur 21 to engage in the' conductor of the lead. The upper portion ofthe bore of extension 24 is flared as at 28 to receive the lower end of a conical rubber washer 29. Thevu'pper end of ring nut I9 is likewise provided with a tubular extension 30 surrounding the extension 24 and threaded at its upper end for the reception of a cap 3|. Cal) 3| will serve to compress washer 29, and this compression will serve to lock the lead 26 in position in the plug and will also serve through the frictional engagement to lock the cap 3l in position.

Since the construction illustrated is capable of considerable modication without departing from the spirit of my invention, I ddnot wish to be understood as limiting myself thereto except as hereinafter claimed.

I claim:

1. In a 'spark plug, a shell having a cylindrical bore, a unitary porcelain comprising a heavy body portion having a thin skirt closely fitting in the bore and in good heat .exchange relation tothe shell, the bore being reduced at its lower end to provide a flange having the same interior diameter as and shielding the lower end of the skirt from direct contact by the products of combustion in an engine, and a large primary electrode detachably engaged in the body portion of said porcelain and filling a substantial portion of' the cavity formed by said skirt and ange to determine the combustion space in the plug and thereby control the heating of the skirt of said porcelain.-

2. In a spark plug, a shell having a cylindrical bore, a unitary porcelain comprising a heavy body portion having a thin depending skirt closely tof the cavity formed by said skirt and liange to determine the combustion space in the plug, said body portion having a shouldered portion whereby it may be clamped in position in the shell, the

periphery of said body portion being in good heat exchange relation with the shell.

3. In a vspark plug, a shell having a cylindrical bore, a unitary porcelain comprising a heavy body portion having a thin depending skirt closely tting in the bore and in good heat exchange relation to the shell, the bore being reduced at its lower end to provide a iiange having the same interior diameter as and shielding the lower end ofthe skirt from direct contact by the products of combustion in an engine. a large primary electrode engaged only in the body portion of said porcelain and lling a substantial portion of the cavity formed 'by said skirt and flange to determine the combustion space in the plug, said body portion having a shouldered portion whereby it may be clamped in position in the shell, the periphery of said body portion being in good heat exchange relation with the shell, a ring nut clamping the porcelain in the shell., the upper end of the body of the porcelain having a sleeve- 'like extension forming a housing for a lead wire ting in the bore and in good heat exchange relation to the shell, the bore being reduced at its lower end to provide a iiange having the same interior diameter as and shielding the lower end of the skirt from direct contact by the products of combustion in an engine, a large primary electrode engaged only in the body portion of said porcelain and filling a substantial portion of the cavity formed by said skirt and ange to determine the combustion space in the plug, said body portion having a shouldered portion whereby it may be clamped in position inthe shell, the periphery of said body portion being in good heat exchange relation with the shell, a ring vnut clamping the porcelain in the shell, the upper end of the body of the porcelain having a sleevelike extension forming a housing for a lead wire to said electrode, said ring nut having a sleevelike extension loosely surrounding the extension of the porcelain, a caphaving threaded engagement with the upper end of the extension of the ring nut and having an opening for the passage of the lead wire, the mouth of the extension of the porcelain being flared, and a conical rubber washer seated in said mouth and engaged b'y said GEORGE PARIQN 

